1. Field of the Invention
This invention relates generally to the field of cannulas and more specifically to such cannulas designed for use in cataract removal surgery.
2. Description of the Related Art
Cannulas consisting of two concentric hollow tubes are known in the art. Such cannulas which utilize one of the tubes for aspiration and one of the tube for irrigation are also known. Some such cannulas are equipped with special tips to assist in the polishing operation of the cataract removal surgery. One example of such a cannula is U.S. Pat. No. 3,589,363 to Banko. Additionally, U.S. Pat. No. 4,428,748 to Peyman, et al. discloses a surgical apparatus which provides a cutting tube as well as an ultrasonic motor for driving a needle with ultrasound.
One common problem with such surgical instruments was the difficulty encountered in sterilizing them. In U.S. Pat. No. 4,573,979 to Blake, the outer cannula is disposable while the inner cannula must be sterilized and reused.
Another problem encountered in the art has been the complexity and expense of machines required to control the aspiration and irrigation rates through the cannula. One example of such machine is disclosed in U.S. Pat. No. 4,764,165 to Reimels, et al. One low cost, simple alternative to the more expensive, complicated aspirator/irrigating machines is disclosed in U.S. Pat. No. 4,320,761 to Haddad.
While cataract removal surgery is a common surgical procedure with acceptable success rates, certain problems and deficiencies remain in the surgical apparatuses and cannulas presently used. The need to sterilize the cannulas results in extra cost as well as problems with infection. Because the concentric hollow tubes are so close together, potential for infection remains despite concerted efforts to effectively sterilize the cannula.
Further, the expensive and complicated irrigation/aspiration machines greatly increase the cost of equipment necessary to perform this operation.
Additionally, large amounts of irrigating media, such as saline solution, are often associated with such machines. Some feel this large amount of irrigating media is unnecessary and unhealthy to the patient.
Further, in some patients the cataracts return, a phenomenon known as "after cataract". With some removal mechanisms, the occurrence of after cataract is as high as 20%.
Finally, in some form of cataracts, the tips associated with current devices are unsatisfactory in removing hardened calcifications in the eye. The current invention overcomes each of these deficiencies in some measure.